1. Field of the Invention
This invention pertains to an in-service activator for booting up switchers in a standby system of a broadband exchanger having a dual system structure.
2. Description of the Related Arts
With recent wide-spread use of data communications, public lines have been carrying not only traditional voice messages but also other vital data in general, communication networks of the future must provide even more accurate transmissions and higher-quality exchanges.
A broadband ISDN (B-ISDN) has been realized as a communication network capable of handling high speed data transferred at a rate in the range of one hundred fifty mega bits per second [150 Mbps] to six hundred mega bits per second [600 Mbps], and various interfaces are being standardized. The CCITT has studied an asynchronous transfer mode (ATM) transmission system.
For instance, a broadband exchanger of an ATM transmission system transmits and exchanges data transported in different bands by splitting them into pieces (called cells) of information having a fixed length of a few tens of bytes. A cell has a header for storing information such as a virtual channel identifier (VCI) which provides information to a subscriber on the receiving side. Hardware of an ATM switcher transmits and exchanges cells to a subscriber which receives the cells at a high speed by using a header. This enables transmission paths to be utilized efficiently by flexibly performing a service requiring different transmission speeds.
In the above described switching operation, the processor of an ATM exchanger designates a memory buffer of a switcher in the switching module in which each cell is to be laid up. Because a cell flows autonomously in the network, this arrangement of a cell switching operation is called self-routing. A subscriber extracts necessary cells by their VCIs from an ATM highway and restores payload data (user-originated information) by eliminating their headers.
FIG. 1 is a block diagram of a communications route in an ATM exchanger.
Each of trunks 2 accommodates a corresponding one of subscriber lines 1 on the input side. A virtual channel controller (VCC) 5 receives outputs from the trunks 2. Based on the call control information from the processor of the ATM exchanger, the VCC 5 reattaches VCIs in the headers of cells supplied from subscriber lines 1 through the trunks 2 by changing them from the ones giving information on their current destinations, i.e. current output nodes (ATM switcher), to the ones giving information on their next destinations, i.e. next output nodes (ATM switcher), and attaches at the head ends of those cells tags giving information on the switching paths within a multistage self-routing module (MSSR) 6 to target output highways 8. A plurality of multiplexer (MUXs) 3 partially multiplex outputs from the VCC 5. Input highways 4 carry corresponding outputs from the MUXs 3.
The MSSR 6 forming substantive communications paths receives outputs from the MUXs 3 through input highways 4.
The MSSR 6 outputs cells through output highways 8 to corresponding demultiplexers (DMUXs) 9, which demultiplex them for outputs through corresponding trunks 7 to subscriber lines 1' on the output side.
As described earlier, a broadband exchanger such as an ATM exchanger must be highly reliable. This is because the transmission capacity of such an exchanger is so large, that its failure may paralyze all the connected systems.
Hence, a broadband exchanger has a dual system structure for meeting the high reliability requirement. One [1] system in the dual system structure ordinarily calls the other system in the same dual system structure a mate system. A system in active use called an active system is backed up by a system in reserve called a standby system in a dual system structure. Thus, usually, the standby system is the mate system for the active system, and the active system is the mate system for the standby system.
A processing by an active system to put the mate system from an out-of-service [OUS] status (standing-by as a backup with no paths set in its switchers) to an in-service [INS] status (actually performing services) is called an INS processing.
When the active system in such a duplex structure system cannot continue its service for one reason (e.g. a breakdown) or another, the INS processing is executed to boot up its mate system, i.e. the standby system, to an in-service status. The INS processing must be executed as fast as possible to minimize a temporary system suspension.
Because a failure occurring in a standby system cannot be detected at all times, its normality is monitored by intermittent checkups.
That is, for confirming each of the two [2] systems (system #0 and system #1) of a broadband exchanger having a dual system structure is normal, a central controller regularly checks them with a diagnostic program. If system #0 is in active use backed up by system #1 in reserve, the central controller diagnoses system #1 in reserve by booting it up from the out-of-service status to the in-service status.
An INS processing system is sought after for promptly performing an INS processing without an increase in load on the central controller.
FIG. 2 is a block diagram of a broadband exchanger pursuant to a prior art example.
A broadband exchanger 100A has a dual system structure. Channel converters 10a, . . . and 10b and 11a, . . . and 11b give channel setting information for routing cells inputted from lines and comprise tables for storing channel setting information. Switchers 20 and 21 form paths designated by channel setting information set by the channel converters 10a, . . . and 10b and 11a, . . . and 11b. Central controllers 30 and 31 execute switching processes. Switch accessors 40 and 41 exchange control information between the channel converters 10a, . . . and 10b and 11a, . . . and 11b and the central controllers 30 and 31. The parts numbered zero [0] at the least significant bit are for system #0 in active use and the parts numbered one [1] at the least significant bit are for system #1 in reserve.
Switcher 20 is in an in-service status and switcher 21 is in an out-of-service status. The system currently in use is called an active system.
Central controller 30 sets to switcher 21 the same paths as those set in switcher 20 by sending commands to channel converters 11a, . . . and 11b and boots up switcher 21 from an out-of-service status to an in-service status, thereby setting the same paths as the active system. This allows the same processings, such as failure supervisions.
According to the prior art example shown in FIG. 2, the channel setting information written in the head end of a cell inputted from a line is analyzed for setting the necessary paths in switcher 20. The channel setting information is stored in the tables of channel converters 10a, . . . and 10b.
That is, the tables of channel converters 10a, . . . and 10b of system #0 in active use (i.e. the act system) respectively store paths, i.e. arteries, within switcher 20. The tables of channel converters 11a, . . . and 11b of system #1 in reserve (i.e. the standby system) store the same contents of the tables of channel converters 10a, . . . and 10b of system #0 in active use. This enables the standby system, which is the mate system of the active system, to operate in the same manner as the active system.
When the earlier described INS processing is performed, the contents in the tables of channel converters 10a, . . . and 10b of system #0 in active use are copied to the tables of channel converters 11a, . . . and 11b of system #1 in reserve. Then, switcher 21 sets paths for switching cells pursuant to the contents of the tables of channel converters 11a, . . . and 11b.
Therefore, to boot up switcher 21 from an out-of-service status to an in-service status, central controller 30 sends to switch accessor 41 commands for setting the same number of paths as that of the paths set in switcher 20 of system #0 in active use.
Therefore, the larger the size of a conventional exchanger, the more time it takes for software processing. This not only lowers the throughput of central controller 30 for other processings but also requires a large amount of time for an INS processing itself.